Brain Teaser: Can you find the number that will replace the question mark in this puzzle?

Are you a maths whiz? If so, can you solve this brain teaser without using pen and paper or even a calculator?

An ‘easy’ brain teaser was shared on microblogging platform X, and it sparked a conversation about the correct answer. The teaser challenges people to guess the number that will replace the question mark. Are you a maths whiz? If so, can you solve this one without using pen and paper or even a calculator?

Brain Teaser: Can you solve this using mental calculations? (X/@Rainmaker1973)

Read| This viral maths brain teaser has started a debate on X. Will you be able to solve it?

“Can you solve today’s easy brain teaser?” reads the caption written alongside the brain teaser shared on X handle @Rainmaker1973. The brain teaser shows an array of numbers written horizontally and vertically. All you need is to find the missing number. Do you think you can solve this one?

Take a look at the brain teaser here:

The brain teaser was shared on March 20 on X. It has since then collected over 3.6 lakh views and the numbers are still increasing. Many even took to the comments section of the post to share their thoughts.

Check out how people reacted to this brain teaser:

“40 is the answer. Pattern for each row: Number 3 = (square root of Number 1×sqaure root of Number 2),” posted an individual.

Another added, “This one is easy, 40. I knew the second I saw 81. You don’t pick 81 out of the blue with 4 next to it.”

“The answer is 40! As the pattern tells you that the third row is the product of the square root of the first two rows. So: 2 x 9 = 18, 6 x 7 = 42, 8 x 5 = 40,” shared a third.

A fourth commented, “The answer is 10. Any other answer apart from 10 is wrong.”

“Answer is 40. Square root the first two, then multiply the results,” wrote a fifth.

A sixth joined, “Multiply the square roots of the first two columns to get the third column.”